92L still a threat to develop; record SSTs continue in the tropical Atlantic

By: Dr. Jeff Masters , 13:44 GMT le 10 septembre 2010

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A tropical disturbance (92L) over the Lesser Antilles Islands lost most of its heavy thunderstorms last night, due to an infusion of dry air. However, 92L has redeveloped a moderate amount of heavy thunderstorm activity this morning, and remains a threat to the Caribbean--though not as great a threat as it appeared yesterday. Satellite loops show that 92L's heavy thunderstorms are slowly growing in areal coverage, and are becoming more organized. St. Lucia reported sustained winds of 33 mph this morning in a heavy rain squall, and heavy rain showers and gusty winds can be expected throughout the southern Lesser Antilles Islands today. Martinique radar shows that heavy rains are now affecting that island, but there is no rotation to the radar echoes evident. Surface observations indicate that pressures continue to fall at a number of stations in the Lesser Antilles, but no surface circulation is evident in the wind reports. A strong flow of upper level easterly winds is creating a moderate 10 - 20 knots of wind shear on the south side of 92L. The waters are at near-record warmth, 30°C, and these warm waters extend to great depth. Water vapor satellite loops show a large area of dry air lies over the northern Caribbean, and this dry air could interfere with development over the next few days.

Forecast for 92L
The disturbance is moving westward at 5 mph, but steering currents favor a more west-northwest motion Saturday. Lower shear lies over the Central Caribbean, away from the coast of South America, so any northward component of motion will allow for more significant development. There is drier air to the north, but 92L is steadily moistening the atmosphere in the Caribbean, so dry air may not be a problem for it. Model support for development is less than it was yesterday. The GFS and NOGAPS models do not develop 92L. The HWRF, GFDL, and UKMET models predict development, with a track taking 92L into the Dominican Republic on Sunday as Tropical Storm Julia. These models predict the storm will continue west-northwest, affecting Haiti, Eastern Cuba, Jamaica, and the Southeast Bahamas early next week. The ECMWF model foresees a more southerly track, taking 92L into Mexico's Yucatan Peninsula seven days from now.

Residents of the northern Lesser Antilles Islands and Puerto Rico should anticipate the possibility of heavy rains from 92L affecting their islands on Saturday and Sunday, though most of the action will probably stay south and west. The southern Dominican Republic should see heavy rains of 3 - 6 inches on Sunday and Monday from 92L, and Haiti, Jamaica, and eastern Cuba should anticipate similar rains on Monday and Tuesday. Should 92L make a direct hit on the Dominican Republic, it could destroy the storm, though. NHC is giving 92L a 40% chance of developing into a tropical depression by Sunday, which is a reasonable forecast. The first Air Force Hurricane Hunter mission into 92L is scheduled for Saturday morning, but there will be two research missions into the storm today that will give us valuable information on 92L's large scale environment and potential for development.


Figure 1. Morning satellite image of 92L.

Igor
Tropical Depression Igor has survived a bout with high wind shear, and is now in an environment of moderate 10 - 20 knots of shear that should allow for steady strengthening. Waters are warm, 28°C, and the Saharan Air Layer (SAL) is probably not close enough to Igor to prevent development. The models continue to predict development of Igor into a hurricane 2 - 4 days from now. Igor will track west to west-northwest over the next week, with long range forecasts from the GFS and ECMWF models putting the storm several hundred miles northeast of the Lesser Antilles Islands about 6 - 8 days from now. Climatology shows that about 10% of all tropical cyclones that have existed at Igor's current position have gone on to hit the U.S. East Coast; these odds are about 5% for Canada. The forecast steering pattern for the coming two weeks from the GFS model shows a continuation of the pattern we've seen all hurricane season, with regular strong troughs of low pressure moving off the U.S. East Coast. This pattern favors Igor eventually recurving out to sea without affecting any land areas. The odds of Igor hitting land in the U.S. or Canada are probably close to their climatological 10% and 5% probabilities, respectively.

Elsewhere in the tropics
The GFS and ECMWF models predict the development of a new tropical wave off the coast of Africa 3 - 6 days from now.

August SSTs in the tropical Atlantic set a new record
Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes had their warmest August on record, according to an analysis I did of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. SSTs in the Main Development Region (10°N to 20°N and 20°W to 80°W) were 1.23°C above average during August, beating the previous record of 1.01°C set in August 2005. August 2010 was the 7th straight record warm month in the tropical Atlantic. The five warmest months in history for the tropical Atlantic have all occurred this year; June 2005 comes in sixth place, and August 2010 in seventh. As I explained in detail in a post on record February SSTs in the Atlantic, the Arctic Oscillation (AO) and its close cousin, the North Atlantic Oscillation (NAO), are in large part to blame for the record SSTs, though global warming and Atlantic Multidecadal Oscillation (AMO) also play a role.

The Bermuda-Azores High was weaker than average during August, which drove slower than usual trade winds over the tropical Atlantic. These lower trade wind speeds stirred up less cold waters from the depths than usual, and caused less evaporational cooling than usual, allowing August SSTs to remain at record warm levels. The Bermuda-Azores High and its associated trade winds are forecast to be at near-average strength during the next two weeks, according to the latest run of the GFS model. This means that Atlantic SST anomalies will continue to stay at record warm levels during September, significantly increasing the odds of major hurricanes in the Atlantic.


Figure 2. The departure of sea surface temperature (SST) from average for September 9, 2010. Note the area of cool anomalies off the U.S. East Coast, due to the passage of Hurricane Earl. Cool anomalies are also evident east of Bermuda, due to the passage of Hurricane Danielle. Image credit: NOAA/NESDIS.

Next post
I'll have an update Saturday morning.

Jeff Masters

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407. IKE
12Z NOGAPS...Link
Member Since: 9 juin 2005 Posts: 23 Comments: 37858
Quoting InTheCone:


And just wait till the little westcasters get home from school, won't they just be so happy with a whole weekend to cry "Trof, what trof, we're all DOOM!"


Well, at least it's only a 2 day weekend for them. ;-)


Oh and Levi...excellent work as always!! :-)
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Quoting Caribbeanislands101:
there's a weak circulation SW of Barbados
That is where I see it too but it is easier to see on shortwave.
Member Since: 9 octobre 2008 Posts: 0 Comments: 8391
So after sept 16 no cape verde storm has made it to US.So much for pattern change if it has no bearing on these storms.
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402. TGTTX
Quoting angiest:


This is what tropical storm Frances did in Houston (after making landfall near Corpus Christi)





Most people seem to have forgotten this storm.


Allison and Ike erased older memories, I reckon'.
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I think the answer to your question is that we are in a La Nina state right now which promotes drier and more stable air.

that is why you have seen overall florida's rain chances and overall rain so much less is that we are in a dry pattern due to the upper atmosphere change from last year when we were in an El Nino. El Nino brings cooler and wetter weather. Of course, in Florida, no real such thing as cool in summer. All this means is that there has been and is more High pressure which brings stable air and a stable upper level environment.

someone please correct me if I am wrong.
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Quoting Jedkins01:
Theres something seriously wrong with the atmosphere over Florida, how can we have 2.34 inch PWATS and barely achieve isolated storm coverage. We have had moisture levels between 2.2 and 2.8 all summer, yet somehow we have seen very little strong thunderstorm activity this summer compared to what is normal, I have yet to see a severe cell yet in my area, yet we normally see lots of severe thunderstorms in the afternoon sea breeze this time of year.

What is the culprit? never ending warm air aloft!

Its ironic whats limiting strong storms in Florida is not moisture, we have tons of it, but its not cool enough up high to get a big storm! lol

What bothers me is this unusually stable upper atmosphere has dominated Florida for months now, something just isn't right.


Interesting, I have been wondering the same thing(WPB), we have gotten lots of rain as of late, but mostly overnight and in the morning. What showers we get in the afternoon have not been too strong/severe. Warm air aloft would certainly explain alot.
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398. IKE
Quoting angiest:


In other words, you have had a persistent capping inversion in place...


I haven't had a drop of rain this month...inland Florida panhandle.
Member Since: 9 juin 2005 Posts: 23 Comments: 37858
Quoting Jedkins01:
Theres something seriously wrong with the atmosphere over Florida, how can we have 2.34 inch PWATS and barely achieve isolated storm coverage. We have had moisture levels between 2.2 and 2.8 all summer, yet somehow we have seen very little strong thunderstorm activity this summer compared to what is normal, I have yet to see a severe cell yet in my area, yet we normally see lots of severe thunderstorms in the afternoon sea breeze this time of year.

What is the culprit? never ending warm air aloft!

Its ironic whats limiting strong storms in Florida is not moisture, we have tons of it, but its not cool enough up high to get a big storm! lol

What bothers me is this unusually stable upper atmosphere has dominated Florida for months now, something just isn't right.


In other words, you have had a persistent capping inversion in place...
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396. JRRP
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395. IKE
12Z CMC....Link
Member Since: 9 juin 2005 Posts: 23 Comments: 37858
Thank you Levi, very good as always.
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Quoting flsky:

Sorry, still can't see the spin. Would please give me the L/L where you are seeing it? Thanks!
there's a weak circulation SW of Barbados
Member Since: Posts: Comments:
Theres something seriously wrong with the atmosphere over Florida, how can we have 2.34 inch PWATS and barely achieve isolated storm coverage. We have had moisture levels between 2.2 and 2.8 all summer, yet somehow we have seen very little strong thunderstorm activity this summer compared to what is normal, I have yet to see a severe cell yet in my area, yet we normally see lots of severe thunderstorms in the afternoon sea breeze this time of year.

What is the culprit? never ending warm air aloft!

Its ironic whats limiting strong storms in Florida is not moisture, we have tons of it, but its not cool enough up high to get a big storm! lol

What bothers me is this unusually stable upper atmosphere has dominated Florida for months now, something just isn't right.
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Quoting angiest:


Cue the comments about an eye forming.


.
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"GFDL is a 10-15 year old model scheme updated intermittently during that time, but not much recently. It is at the mercy of the GFS boundary and initial conditions + it's own bogus. It's the "cork in a stream" model. It will intensity everything and anything, even over land and terrain. It's nuts.

HWRF is an unmitigated disaster and embarrassment for NCEP //at this point// in the time. It has potential but the man hours and effort put into it is insufficient. It has suffered from a multitude of problems ... (not going to discuss).

The ECMWF global model is probably better than all of them since it's global resolution is 14-16 km which is about the finest scale to use cumulus parameterizations (maybe 9-10 km is the limit). Otherwise, cloud resolving models for global forecasting are at least 3-years away -- and ECMWF should do it as Moore's Law stays intact and petascale computering becomes the norm."
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1985, Gloria developed on September 16th and hit the United States


in general the CV season shuts down after the 3rd week of September, so saying that after September 16th no CV storms have hit the US; doesn't really prove anything.
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oh ok. so, this info is only for long track CVS's? Meaning the correlation in octants and direction here is specfically for african based storms headed west.

how can we read the same charts you posted but for storms that form closer to home? thanks
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Quoting Neapolitan:
Just for fun, I went back and looked at the action on "peak day" on the six most active seasons in the past 15 years:

1995: Hurricane Luis weakened to a Cat 1 north of Bermuda.

1998: Francis was a minimal TS drifting around the western GOM.

1999: TS Floyd grew into a Cat 1 hurricane north of the Windward Islands.

2003: Cat 3 Hurricane Isabel became a Cat 4 in the central Atlantic.

2004: Hurricane Ivan was a Cat 4 storm just north of Venezuela.

2005: Two tropical storms--Maria and Nate--became extra-tropical, while TS Ophelia became a minimal Cat 1.

2010: TS Igor is growing in the eastern Atlantic.


This is what tropical storm Frances did in Houston (after making landfall near Corpus Christi)





Most people seem to have forgotten this storm.
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Agree with yoo Ike...The west Carib. will probably bring multiple threats to Florida IMO.
The Atlantic seems destined to re-curve and later on those troughs will be more frequent then now....


Quoting IKE:


All I'm saying is...look closer to home....real soon. There's little to no chance of another Igor developing where he's at now after Sept. 16th that will impact the USA.

The hot spot is fixing to be the western Caribbean...climatology says so....







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Quoting CaicosRetiredSailor:
Igor's more modest now:



Very nice outflow, expecially the south. Most of the circulation, if not all, is already under the convection
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382. flsky
Quoting Goldenblack:
Look at the visible satellite, you will see spin:

Visible Satellite Loop



Sorry, still can't see the spin. Would please give me the L/L where you are seeing it? Thanks!
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i'm starving. going to pick up an italian sub. bbl
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Nao and Mjo did this earlier and everything went out to sea,why would this change now?
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Quoting Caribbeanislands101:
what;s that island east of Igor?


Thats just a hump.
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Quoting CaicosRetiredSailor:


Cue the comments about an eye forming.
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376. IKE
Quoting Thaale:

So you're saying that we're way overdue...black has come up umpteen times in a row. Mortgage the house and bet it all on red! ;)


All I'm saying is...look closer to home....real soon. There's little to no chance of another Igor developing where he's at now after Sept. 16th that will impact the USA.

The hot spot is fixing to be the western Caribbean...climatology says so....







Member Since: 9 juin 2005 Posts: 23 Comments: 37858
wow that is a small field of winds considering the size of the convection!

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Quoting kshipre1:
oh, ok. thanks storm. this is interesting stuff. so, given the recurves we have had of late, right at 60W, we are in a neutral state. Once, in octants 1 and 2, depending on the ridge (if further west towards SE USA), should steer storms further west?
I'm not storm but i think that's what he meant
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Just for fun, I went back and looked at the action on "peak day" on the six most active seasons in the past 15 years:

1995: Hurricane Luis weakened to a Cat 1 north of Bermuda.

1998: Francis was a minimal TS drifting around the western GOM.

1999: TS Floyd grew into a Cat 1 hurricane north of the Windward Islands.

2003: Cat 3 Hurricane Isabel became a Cat 4 in the central Atlantic.

2004: Hurricane Ivan was a Cat 4 storm just north of Venezuela.

2005: Two tropical storms--Maria and Nate--became extra-tropical, while TS Ophelia became a minimal Cat 1.

2010: TS Igor is growing in the eastern Atlantic.
Member Since: 8 novembre 2009 Posts: 4 Comments: 13549
Quoting Thaale:

So you're saying that we're way overdue...black has come up umpteen times in a row. Mortgage the house and bet it all on red! ;)


Wow a whole 20 years!!!

well I guess the US wont get another CV threat in 2010
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Quoting CaicosRetiredSailor:
what;s that island east of Igor?
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Quoting StormW:


Not with a shift in the MJO and NAO.


ok. so those waves that are currently still on Africa, but that will be coming off in the next 7 to 10 days (when the MJO is in the dashed octants) will potentially have a chance to enter the GOM because the trough/ recurve set up will be no more in about 7 to 10 days.
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Quoting Caribbeanislands101:
Survey or Poll
Will Invest 92L turn into tropical storm Julia?

A for yes
B for No

B
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..oops image I posted was old
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Survey or Poll
Will Invest 92L turn into tropical storm Julia?

A for yes
B for No
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oh, ok. thanks storm. this is interesting stuff. so, given the recurves we have had of late, right at 60W, we are in a neutral state. Once, in octants 1 and 2, depending on the ridge (if further west towards SE USA), should steer storms further west?
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Quoting Goldenblack:
I don't think that was what he was saying about Igor.....

yeah i think it was, but it should recurve north around 50w
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Quoting IKE:
I went back and checked....back to 1990...the last 20 years of the Atlantic tropical season......

Since 1990...from September 16th of each year on, the number of named systems that have formed(at least as a tropical storm), BEFORE 40W, that made lower 48 landfall......zero.

So you're saying that we're way overdue...black has come up umpteen times in a row. Mortgage the house and bet it all on red! ;)
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Quoting StormW:


In about 7-10 days, which will work hand in hand with the NAO change.
that's also the time frame when 3 more waves come off the african coast
yikes!!!!!!!
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You are right leo, that is why I stated a few posts back that we should see what Dmax tonight does for 92L.

Quoting leo305:
btw..

when a storm system looks "weak" during the day, I've noticed that if it has a spin, and it has a lot of moisture around, and the area around it can get heated up for sun down, DMAX has a huge effect on it
Member Since: 28 juin 2010 Posts: 0 Comments: 706
Quoting StormW:


That's correct.

That's why you can see the trof coming off the east coast.



but this is not what you expect to continue?
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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